Refining of brass



Aug. 1, 1933.

c. A. ROSE El AL 1,920,820

REFINING OF BRASS Filed May 24. 1930 SCRAP BRASS ICAST INTOIANODESELECTROLYZE SULPHATE SOLUTION OF CU,ZN

Cu Pb, SM CATHODE SUMES .CONTINUALLY WITH- DQAW ELECTROLYTE nacoven IMETAL VALUES I EVAPORATE] I COOL Q I MOTHEQ'L'QUOR z-so CRYSTALS E'DISSOLVE Cu 0 H 50 ATTORNEY Patented Aug. 1, 1933 UNITED STATES PATENTOFFICE REFINING F BRASS Application May 24, 1930. Serial No. 455,168-

2 Claims.

This invention relates to the process of treating scrap brass forrecovering copper and zinc therefrom, and more particularly to anelectrolytic process in which the copper is recovered as cathode 5copper and the zinc is recoveredin the form of zinc sulphate crystals.

The invention provides a process of the above nature which issubstantially continuous and is carried out without the formation ofundesirable by-products. The electrolyte is largely recovered andrecirculated through the cells, so that the copper andzinc content ofthe active electrolyte is maintained substantially constant and thespent electrolyte, after the recovery of copper and zinc therefrom, isagain utilized in the cyclic operation. The zinc is recovered in theform of crystals which may be purified or may be marketed as the finalproduct.

The invention further consists in the new and novel features ofoperation and the new and orig- I inal arrangements and combinations ofsteps in the process hereinafter described and more particularly setforth in the claims. r

In the accompanying drawing the figure is a fiow sheet illustrating thesteps of the present process.

Although the novel features which are believed to be characteristic ofthis invention will be particularly pointed out in the claims app'endedhereto, the invention itself, as to its objects and advantages, the modeof its operation and the manner ofits organization may be betterunderstood by referring to the following description in which aparticular commercial embodiment thereof is disclosed. It will beunderstood, however, that the processes and the steps thereof may bemodified in various respects without departing from the broadfspirit andscope of the invention.-

In the following description and inthe claims the various steps in theprocess and the details comprising the invention will be identified byspecific names for convenience, but they are intended to be as genericintheir application as the art will permit.

In accordance with the present invention the brass is cast into anodeswhich are electrolyzed in asulphate solution containing a predeterminedamount of copper and zinc; The copper is deposited on the cathodes andis removed aselectrolytic copper. The copper and zinc content of theelectrolyte is maintained within the desired range by constantlywithdrawing a portion thereof in which the copper is depleted and thezinc con- 55 tent increased and adding additional quantities Y cathodes.

free sulphuric acid per of electrolyte having the original zinc andcopper content.- This additional electrolyte is derived from asubsequent step in the process.

-The electrolyte which is withdrawn is concentrated and cooled tocrystallize the zinc as zinc sulphate crystals which are removed andsold to the trade or treated byany desired purification process. Themother liquor, after the removal of the crystals, is diluted to itsoriginal volume and copper is added to increase the cop per content tothat of the original electrolyte, after which it is introduced into thecells in the step above mentioned.

As a specific manner of carrying on the above process, the scrap brassis cast into anodes which are electrolyzed in cells through which anelec-- trolyte containing given percentages of copper and zinc and freesulphuric acid is continually circulated. v During this electrolysis thecopper content of the electrolyte is continually depleted and the zinccontent increased owing to the fact that both copper and zinc aredissolved from the anodes, whereas copper only is deposited at the Theweight of copper deposited is so approximately equivalent to the amountof cop-- per and zinc which is dissolved from the anodes.

The electrolytic cells may be arranged so that the electrolyte flowsthrough all of the cells in parallel, in which case the composition ofthe electrolyte will be the same in all cells. The cells may, however,be arranged in parallel groups, the cells of each group being arrangedin cascade. In this case the incoming solution of high copper and lowzinc content is applied to the upper cell of each series and flowsthrough the cells of the series until it overflows from the lowest.During this passage through the cells the copper content is depleted andthe zinc content increased to the point desired for the next step. '95

As a specific example, the solution which is fed into the upper cell maycontain 75 grams copper per liter, 40 grams zinc per liter and gramsfree sulphuric acid per liter. The solution overflowing from the lowestcell may contain 100 15 grams copper, 100 grams zinc and 100 gramsliter. The copper content of the solution withdrawn from the cells willbe governed largely by the minimum con-.

tent with which'a firm coherent cathode deposit of copper can beobtained.

The electrolyte withdrawn from the cells is treated for the recovery-ofthe zinc content by being evaporated to sucha volume that when cooled itwill be "super-saturated with zinc sulphate, but not super-saturatedwith copper sulphate.

The solution is then cooled to any convenient temperature, such as 20 C.and a portion of the zinc sulphate is allowed to crystallize out as zincsulphate crystals. The amount of zinc sulphate which will crystallizeout will depend upon the composition of the solution before evaporationand the relative volumes before and after evaporation. The evaporationshould be carried to such a point that the weight of zinc contained inthe crystals is approximately equal to the weight of zinc dissolved fromthe brass anodes in the electrolytic cells.

The zinc sulphate crystals may contain slight amounts of copper sulphateand other impurities and may be purified in any suitable manner. Ifdesired, they may be marketed as crude zinc sulphate crystals. Thecrystals may be dissolved in water and the resultant solution purifiedby well known methods and either electrolyzed with insoluble anodes forthe recovery of electrolytic zinc or evaporated for the recovery of purezinc sulphate.

The mother liquor, after separation of the crude zinc sulphate crystals,is diluted with water to its .original volume. It should then containapproximately the same amount of copper as the electrolyte drawn fromthe cells and about the same amount of zinc as the solution originallyapplied to the cells.

The copper content of the solution is thenincreased to that of theoriginal solution, for example, 75 grams per liter, by dissolving coppersulphate or copper oxide therein, or by circulating it through finelydivided metallic copper in the presence of air. If copper oxide ormetallic copper is used an equivalent amount of sulphuric acid must alsobe added to maintain the acid content of the solution constant.

The solution then contains approximately 75 grams copper, 40 grams zincand 100 grams of sulphuric acid per liter and is recirculated by beingapplied to the electrolytic cells thereby completing the cycle. a

Any impurities, such as lead and tin, in the scrap brass may berecovered as anode slimes from the electrolytic cells and may be treatedin any well known process for the recovery of the metal valuestherefrom.

Although certain novel features of the invention have been described andare pointed out in the annexed claims, it will be understood thatvarious omissions, substitutions and changes in the'se'veral steps ofthe process and in its operation may be made by those skilled in the artwithout departing from the spirit of the invention.

What is claimed is:

1. The process of treating brass which comprises forming said brass intoanodes, treating said anodes in cells containing an electrolyte ofsubstantially 75 grams per liter copper and substantially 40 grams perliter zinc in sulphate solution, continuing said treatment until thezinc content is increased to approximately 100 grams per liter and thecopper is decreased to approximately 15 grams per liter, continuouslywithdrawing portions of the electrolyte of the above concentration andcontinuously adding further corresponding quantities of electrolyte ofthe first mentioned composition, evaporating the portion so withdrawn tocause the same to be supersaturated with zinc sulphate, cooling toapproximately 20 C.,whereby a portion of the zinc sulphate crystallizes,removing the mother liquor, diluting with water to its original volumeand adding copper to bring the copper content to approximately 75 gramsper liter and utilizing the same as the source of electrolyte for saidcells.

2. An electrolytic process for treating brass which comprises formingsaid brass into anodes, electrolyzing said anodes in an electrolytecontaining predetermined amounts of copper and zinc in sulphate.solution for the ,deposition of copper as cathode copper therebydecreasing the copper content and increasing the zinc content of saidelectrolyte, withdrawing portions of said electrolyte, replacing theelectrolyte so withdrawn with substantially equivalent quantities ofelectrolyte having the composition of the initial electrolyte, forming asupersaturated zinc sulphate solution by evaporating the portions ofelectrolyte withdrawn, cooling said supersaturated solution therebycrystallizing out zinc sulphate, diluting the mother liquor tosubstantially the original value, increasing the copper content of saidmother liquor to approximately that of the original electrolyte andrecirculating same to the electrolytic cells.

CHARLES A.. ROSE. BERRY MARVEL OHARRA.

